1. Field of the Invention
The present invention relates to a method and an apparatus for automatically producing bags with openings. More specifically, the invention relates to a machine equipped with a floating separator for automatically producing bags with openings by using a film tube as a blank, the machine being capable of highly efficiently forming split lines in a portion of the film tube, for example, in an upper half portion only of the film tube, to form openings, or forming many small holes at one time.
2. Background Art
A protective bag made of a plastic film such as thermoplastic polyolefin resin film, e.g., polyethylene (PE) or polypropylene (PP) or thermoplastic resin film, e.g., nylon, PVC, PVA, EVA, PS or PET (inclusive of a laminate thereof), used for sheets for automobiles and as other protective covers, has been produced by stacking a large number of, for example, several tens to several hundreds of pieces of films cut into the shape of a sheet one upon the other to form large and small openings, and melt-adhering the required portions.
In the case of producing a bag having asymmetrical openings in the upper and lower surfaces, in particular, double-size blanks are stacked to execute the searing or opening, and the films are folded piece by piece and are melt-adhered.
This conventional method is suited for producing many kinds of bags in small quantities, involving, however, much manual work, resulting in an increase in the cost of production, still accompanied by troubles in quality such as poor openings, poor melt-adhesion and the like. Besides, the yield of production is never high.
Japanese Examined Patent Publication (Kokoku) No. 67414/1993 discloses an improved mechanism for heat-melting and adhesion, according to which two pieces of overlapped synthetic resin films are cut using a heated blade, and the cut ends are melt-adhered together by heating. With this mechanism, however, the two pieces of overlapped films can only be cut and melt-adhered simultaneously without accomplishing such a sophisticated work that a portion of the film or the tubular blank is cut and is opened to melt-adhere at least a portion corresponding to the bottom of the bag. In other words, it was not possible to simultaneously form asymmetrical openings in the upper and lower surfaces of the protective bag.
It is a first object of the present invention to produce protective bags of a plastic film having large and small openings which are symmetrical or asymmetrical in both surfaces at a decreased cost and at a high speed.
It is a second object of the present invention to produce protective bags of a plastic film of stable and high quality, without significant variation in quality, in large quantity.
The present invention is concerned with a method of automatically producing bags with openings by inserting a plate-like floating separator in a film tube blank that moves in the lengthwise direction, the plate-like floating separator being limited from moving in the direction of width and in the direction of progress, and forming openings or executing the melt-adhesion in at least one surface of the film tube blank during an intermittent stoppage of motion of the film tube blank.
In a further embodiment, the invention relates to a method of automatically producing bags with openings as described above, wherein the floating separator is electromagnetically supported, and its movement in the direction of width or in the direction of progress is limited by rolls and/or an endless belt and/or fixed guides.
In a still further embodiment, the invention relates to an apparatus for automatically producing bags with openings comprising a pay-off reel for supplying an intimately adhered film tube blank, a loop device, at least one melt-adhering device, an opening device, a predetermined length-drawing device and a cutting device, wherein a floating separator is inserted in the film tube blank on a side of entering into the opening device, the floating separator being limited from moving in the direction of forward progress of the blank and in the direction of the width of the blank. The floating separator further serves as a cradle for forming openings in at least the upper surface by using an opening punch.
In another embodiment, the invention relates to an apparatus for automatically producing bags with openings, as above, wherein the opening punch is a shearing relief or a heated relief.
In yet another embodiment, the invention relates to an apparatus for automatically producing bags with openings according to one of the above-described embodiments, wherein the searing relief has an opening portion of a relatively wide area for passing a protruded portion of a material packaged in a product bag, and the heated relief has an opening portion of a relatively small area for passing a cord or a rubber cord used for fastening the opening or the periphery of the opening after a material is packaged in the product bag.
In another embodiment, the invention relates to an apparatus for automatically producing bags with openings according to one of the above embodiments, wherein the opening portion is an incomplete opening portion leaving a blank continuing portion in a portion thereof.
In a further embodiment, the invention relates to an apparatus for automatically producing bags with openings according to one of the above embodiments, wherein means for limiting the movement of the floating separator in the direction of progress of the blank is constituted by a pair of upper and lower rolls that are symmetrically arranged to come in contact with the upper and lower surfaces of the blank satisfying a relation T1 greater than T2, wherein T1 is the thickness of the floating separator and T2 is a gap between the rolls.
In a still further embodiment, the present invention relates to an apparatus for automatically producing bags with openings according to one of the above embodiments, wherein means for limiting the movement of the floating separator in the direction of progress of the blank comprises rolls asymmetrically arranged up and down and/or an endless belt and/or fixed guides.
In a yet further embodiment, the present invention relates to an apparatus for automatically producing bags with openings according to the above embodiment, wherein means for limiting the movement of the floating separator and of the film tube blank in the direction of width comprises at least a pair of rollers arranged on the outer sides of the blank in the direction of the width of the blank and pivotally attached to the base plate along a nearly vertical axis and/or an endless belt and/or fixed guides.
In another embodiment, the present invention relates to an apparatus for automatically producing bags with openings according to one of the above embodiments, wherein the melt-welding device is a linear heat welder of one stage or of a plurality of stages.